1. Field of the Invention
The present invention relates to image display apparatuses and, more particularly, to an image display apparatus which projects images relating to the same object onto a screen, and which superimposes the images on the screen using a plurality of projectors.
2. Description of the Related Art
Color management systems (CMSs) that perform color matching of input and output images among a plurality of color image apparatuses such as a color CRT monitor or a color printer are prevailing in a variety of fields that handle color images.
It is known that if a color based on the same tristimulus values XYZ is viewed under different illumination conditions, the color looks different depending on a variation in sense characteristics of humans such as a chromatic adaptation. In the above-mentioned system, the same problem is presented when a reproduced image is viewed under a different illumination condition.
The tristimulus values XYZ are quantitative values defined by the International Commission on Illumination (CIE), and guarantee that a color looks the same under the same illumination conditions. The tristimulus values XYZ cannot be applied to the case where the same color is viewed under different illumination conditions.
To overcome this drawback, the conventional CMS uses a human color perception model such as a chromatic adaptation to reproduce colors that correspond to the tristimulus values, which are viewed the same under different environments. As discussed in the book entitled “Color Appearance Models” by Mark D. Fairchild (Addison Wesley (1998)), several models have been proposed. Studies have been made to establish a model that permits a more precise color prediction. different from the one used during the photographing operation, a spectral reflectivity image of the subject is estimated. The estimated spectral reflectivity image is then multiplied by an illumination spectrum at a viewing side to result in tristimulus values under the viewing illumination, and then the color is reproduced. Since such a technique of illumination conversion is designed to reproduce the tristimulus values when the subject is present under the viewing illumination, precise color appearance is obtained without paying attention to a vision characteristic of humans such as color adaptation.
In one type of image display apparatus, a projection optical system projects an image presented on a display device such as an LCD to a screen by illuminating the display device with light from a light source. A variety of such models have been proposed and are commercially available.
In this type of image display apparatus, a diversity of techniques are introduced to improve the quality of displayed images. For example, in some commercially available and relatively high-end image display apparatuses, identical images, projected by a plurality of projectors, are superimposed on a screen to heighten luminance of the displayed images.
Even for the above mentioned image display apparatus, it is desired to present high-quality images such as an image with a high color reproducibility, a high luminance image, or a stereo-vision image without introducing any particularly complex and costly arrangement.